WASHINGTON - U.S. emissions of carbon dioxide, the main greenhouse gas, should fall 5.9 percent in 2009 as the recession cuts electricity and transportation fuel demand, the government said in a monthly forecast on Tuesday.

Demand for coal, which emits about twice as much carbon dioxide as natural gas per unit of energy generated, should fall more than 9 percent in 2009 on the economic downturn, said the Energy Information Administration, the statistics arm of the Department of Energy, in its short-term forecast.

Several factors contribute to a projected reduction of nearly 6 percent in U.S. carbon dioxide emissions from fossil fuel use in 2009, primarily associated with the economic downturn, EIA Administrator Richard Newell said.

Heavy industry demand for electricity should fall 11 percent in 2009 as manufacturing declines and raw steel production is expected to drop 40 percent.

The EIA slightly narrowed its 2009 emissions forecast. Last month, it predicted the year's emissions would fall 6 percent.

Many power generators are switching to burning natural gas as states crack down on carbon emissions and as Congress mulls climate legislation, which also pushed emissions down.

Weaker demand for transportation fuels, especially jet fuel and diesel for trucks, should account for 30 percent of the annual decline in carbon emissions, the EIA said.

Next year emissions should begin creeping up. The EIA said the projected recovery in the economy should help push emissions up 1.1 percent in 2010.

(Reporting by Timothy Gardner; editing by Jim Marshall)